Development of a new structured interview for the anxiety disorders makes possible a major descriptive study of the DSM-III anxiety disorders. After an extension and enlargement of a preliminary study demonstrating that DSM-III anxiety disorder categories are reliable, the phenomenology of the anxiety disorders will be examined through comprehensive clinical interviews, psychological testing, physiological assessment, and periodic self-monitoring of relevant cognitive and behavioral events. Reliably diagnosed patients in each of the anxiety disorder categories will be interviewed, tested and followed over a period of two years. Similarities and differences among the DSM-III anxiety disorders on crucial psychological and physiological measures will be noted as compared to normals. In addition, similarities and differences between anxiety disorders and other closely related psychopathological states, specifically stress disorders, as represented by chronic headache, and depressive disorders, as represented by major depression, and dysthymic disorder will be ascertained on these measures. The presence of diagnosable anxiety disorders in these populations will be determined. Specifically, 15 patients in each DSM-III anxiety disorder category will be accumulated after interviewing a consecutive series of patients in the Phobia and Anxiety Disorders Clinic, with the sole exception of Post Traumatic Stress Disorder, to confirm and extend preliminary data on reliability of these categories. These 15 patients in each category, including PTSD, will then be compared on interview, psychological test, physiological assessment, and self-monitored cognitive and behavioral data. These data will be compared, in turn, to similar data collected from a group of 30 SADS - diagnosed affective disorders, consisting of 15 major depressives and 15 dysthymics, a group of 15 stress-disordered patients suffering from chronic headaches, and a group of 30 normal subjects. A full description of anxiety-related phenomena in all of these groups will be followed by estimates of the discriminative validity of the individual anxiety disorders from each other and from psychopathologically closely related stress disordered and depressive populations and from normals. Finally, examining anxiety disorders, including PTSD's and normals, periodically over a course of two years will determine the course of these disorders or the predictive validity of the initial diagnosis.